In vivo confocal microscopy in patients with symptomatic diabetic polyneuropathy compared to controls

Abstract

Diabetic neuropathy (DN) is a common clinical condition. The currently recommended diagnostic tests have low sensitivity, such as electromyography or invasive tests, such as skin biopsy. Additional researches of new techniques have been developed in order to identify the early involvement of the peripheral nerve. With the advent of corneal confocal microscopy (CCM) in vivo, it was observed a reduction of corneal innervation in patients with DN. We compared the morphological changes of the sub-basal corneal epithelial plexus through the in vivo CCM in 35 diabetic patients with symptomatic distal symmetric polyneuropathy (DSP), compared to 55 control subjects. Furthermore, we sought to determine a pattern of change between severity stages of DSP, comparing clinical, laboratory, and nerve conduction (NC) variables. Differences between control and diabetic groups were observed for the following variables: age (44.9 ± 13.24 vs 57.02 ± 10.4, p-value < 0.001), fiber density (29.7 ± 10.2 vs 16.6 ± 10.2, p-value < 0.001), number of fibers (4.76 ± 1.30 vs 3.14 ± 1.63, p-value < 0.001), number of Langerhans cells (4.64 ± 8.05 vs 7.49 ± 10.3, p-value = 0.035), tortuosity (p-value < 0.05) and thickness (p-value < 0.05). Furthermore, inverse relationship was found between fiber density and age (p-value <0.01) and fiber density and clinical level (p-value <0.05). We also observed a positive relationship between conduction velocity and peroneal nerve fiber density (p-value < 0.05). We therefore conclude that the CCM is a fast, noninvasive and reproducible method for diagnosis, staging and monitoring of diabetic DSP.